Thermal cut-out for electric circuits.



No. 822,336. PATENTED JUNE 5, 1906.

J. C. ARMCR.

THERMAL CUT-OUT FOR ELECTRIC CIRCUITS. APPLICATION TILED JUNE 3,1903.

mm I 'F:='1lIIIl///////////////////// 15 llllflllllllllllllllllllllliillllllllllllllu UNITED STATES JAMES (J. ARMOB, OF PITTSBURG', PE

PATNT NNSYLVANIA, ASSIGNOR TO GEQRGE THERMAL CUT-GUT FOR ELECTRECClRQlJiTS= Specification of Letters Patent.

Patented June 5, 1906.

Application filed June 8,1903. Serial No. l60,636l

To all whom, it may concern:

Be it known that I, JAMES C. AnMoR, a citizen of the United States, anda resident of Pittsburg, in the county of Allegheny and Stateof'Pennsylvania, have invented a new and useful Improvement in ThermalCut- Outs for Electric Circuits, of which the following is aspecification.

My invention relates to safety devices or cut-outs for electriccircuits; and it has for its object to provide a device of thischaracter which shall embody a substance that is combustible orvaporizable when subjected to a predetermined excessive temperature, andthus becomes effective to open the circuit in which the device isincluded.

While my invention is susceptible of use in any electric circuit, it wasprimarily designed for use in the heater-circuits of electric lamps, thelight-emitting members or glowers of which are non-conductors atordinary tem peratures and are heated to conducting temperature by meansof electric heaters. For convenience the invention will be illustrated ddescribed as embodied in a lamp of the character above indicated, butwithout intention of limiting it to use in such relations.

It is usual to provide the heater-circuits of lamps of the characterabove indicated with cut-outs which are opened by means of coils in theglower-ci'rcuits and which are automatically closed by means of gravityor springs when no current is flowing in the glower-circuit. I

If a lamp contains several glowers, rupture of one of them will ofcourse not interrupt the glower-circuit; but where a single glower isemployed in a lamp, or even where two glowers are employed, it ispossible that the glower-circuit may be interrupted by reason of theburning out or accidental breaking of the glower in case onlyone isemployed, or both in case there are two, and when such accident occursthe heater is automatically cut into circuit, and under the conditionsheretofore existing the current will continue to traverse the heater andwill in time cause serions deteriora ion or actual destruction of thesame unless current is cut off from the lamp.

I propose to eater-circuit rupted,

provide ameaiis whereby the will be automatically intera predeterminedlength of time after cipal operating parts of a lamp provided with myimprovement. Fig. 2 1s a central sectional View taken at right angles.to Fig. 1 and showing the parts on a larger scale Fig. '3 is a detailperspective view, also on an enlarged scale, of the device constitutingthe chief element of my invention.

The lamp here indicated is of the single-- glower type and is suppliedfrom a circuit 1 2, the glower 3 and tubular heaters 4 being supportedin a suitable non-conducting frame 5, such frame being suspended below anonconducting disk 6, which is provided with three contact terminal pins7, 8, and 9, the latter 'making engagement with terminal sockets in thenon-removable portion of the lam (N 0t shown.)

T e pins 7 and 9 constitute glower-terminals, the connection therewithbeing made by means of metal angle-pieces 10 and 11 and removable pins12 and 13, which are respectively connected to the glower terminal wi es14 and 15. The pin 9 also constitutes on; )f the heater-terminals, thepin 8 bein the other heater-terminal, which is fastened to a metal bar16, whereby to the under side of the disk 6.

One end 17 of the bar 16 is bent at substantially right angles to thebody ortion, and seated in a hole therein is the re uced end 15% of asmall rod 19, the other end of'this rod being bored out to form a cavity'20, in which is p aced a piece 21 of material that is combustibleorvaporizable or otherwise produces a sufficient volume of gas to morethan fill the the latter is clamped cavity when subjected to amaintained high temperature. cavity 20, which may be of any desireddepth, is closed by means of a terminal plug 22, to which is fastenedthe end of heater-terminal wire 23.

The rod or tube 19 is located sufiicientiy near the heater-tubes so thatwhen the latter operate for a considerable length or timesay four orfive minutee-the heat generated The outer end of the hole or will besufficient to burn or vaporize the body 21, and thusproduce a suflicientvolume of gas to blow out the lug 22, and since this red is connecteddirect y in the heater circuit when the plug is blown out the saidcircuit will be interrupted.

Any one of a considerable variety of materials orrcompositions ofmaterials may be employed as the combustible or vaporizable substance.One substance which I have employed and found to be satisfactoryconsists of chlorate of potash, powdered charcoal, and a solutionof'silicate of soda mixed together, compressed, or molded into suitableform and dried. The composition may be conveniently forced through asuitable die while in plastic condition, and after the string thusformed is dry it may be readily broxen into short lengths, which areWell adapted to the purposes of my invention,

The heat generated during the time necessary for raising the glower toconducting temperature is not sufficient to vaporize the body 21, andconsequently the heater-circuit remains closed except when opened by thecut-out 24 or when the heater operates a certain predetermined length oftime in excess of that required for raising the glower to conductingtemperature, as will be the case when the glower is broken or thecircuit otherwise interrupted.

Operative means for effecting the result herein specified, which diiferfrom the means here set forth as regards-structural details,

but not as regards mode of operation, I desire to include within thescope of my invention.

I claim as my invention 1. In an electric lamp, the combination with aglower that is a non-conductor at ordinary temperatures, of an electricheater therefor and a thermal cut-out in the heatercircuit comprising asolid-metal body having a cavity in one end thereof, vaporizablematerial in said cavity and a terminal plug removably fitted into oneend of said cavity.

2; In an electric lamp, the combination with a glower that is anon-conductor at ordinary temperatures, of an. electric heater thereforand a thermal cut-out comprising a solid-metal rod having a cylindricalchamber inone end, a body of vaporizable material in said chamber andaterminal plug normally fitted into the outer end of said chamber.

3. The combination in an electric circuit, of a solid-metal rod having acavity in one end and constituting one terminal, a plug fitted into theend of the cavity and constituting the other terminal and a charge ofcom- -bustible or vaporizable material in said cavity that acts to blowout the plug when subjected to a rise of temperature above apredetermined limit.

In testimony whereof I have hereunto subscribed my name this 25th day ofMay, 1903.

JAS. CJARMOR.

lVitnesses EDWARD BENNETT, HUGH A. CRooKs.

